Why Excel struggles with them
Current versions of Excel open few Lotus 1-2-3 or Quattro Pro files, and Numbers and Google Sheets open none. Many of these files hold several sheets (.wk3, .wk4, .123 and every Quattro Pro notebook), and all of them need to come across, not just the first.
How to convert one
Drop the file above. The page reads it with libwps, the reader LibreOffice uses for both programs, and shows every sheet as its own tab, with numbers in the formats the spreadsheet used: currency, percentages, dates and decimals.
"Save as CSV" is free and saves the sheet you're looking at. "Excel file" (part of the one-time unlock) saves the whole file as one .xlsx workbook, one sheet per tab, with numbers and dates as real values so sorting and sums work.
Formulas and macros
Formula cells come across as the values Lotus or Quattro Pro last worked out, so the workbook shows what the original showed. Point at a cell here to see the formula behind it. Lotus macros were stored as text in cells, so you'll see them, but they won't run in Excel.